It's classed as an Alchemy ingredient. It's in "The Alchemist's Crate", although you can't see it in the displayed contents. There seems to be a limit on the number of items the game will display. But, if you empty the entire crate 200 powdered mother of pearl will appear in your craft bag.
Edited by RaddlemanNumber7 on December 16, 2019 8:47AM